Every guitar effects pedal on your pedalboard will make use of an LED (Light Emitting Diode) to signify whether or not the pedal is engaged. Generally, if the LED is illuminated, the pedal is active and in use. 

However, what makes the LED illuminate in the first place and is there anything we can do to change it?

Of course there is! We just need to know a few details about the LED in question. Let’s take a look, shall we?

What Determines How Bright The LED Is In The Effects Pedal?

The amount of current passing through an LED and the direction of that current will determine whether or not the LED lights up and how bright it will be.

Not all LEDs are the same and you will need to investigate the specifications of the LED you’re using to ensure you use the correct current. However, as a general rule of thumb, we can assume that the below LED colours have the following voltages:

Red LED – 1.2 – 2 volts
Orange LED – 2 – 2.1 volts
Yellow LED – 2.1 – 2.2 volts
Green LED – 1.9 – 4 volts
Blue LED – 2.5 – 3.7 volts
Violet LED – 2.8 – 4 volts

Anything less than these voltages and the LED won’t light up. Anything significantly higher than these voltages and the LED may burn out. Therefore, we can’t connect these straight up to our 9 volt power supply. We need to place a resistor in series with the LED as a CLR to lower the voltage before it hits the LED.

It may sound like a fine balancing act, but it all comes down to math. If you do your math, and more specifically follow Ohm’s Law, you shouldn’t have any issues. 

If we take a Red LED with a standard forward voltage of 20mA and requires 1.2 volts, we need to send the remaining 7.8 volts through a resistor to prevent the LED from burning out. Using Ohms Law, we know that to work out the required resistance, we must divide the voltage (7.8 volts) by the current (20mA or 0.02A). This then provides us with the required resistance of 390 Ohms. 

The higher the value of the resistor, the lower the voltage is feeding into the LED and the dimmer the light.

The lower the value of the resistor, the higher the voltage is flowing into the LED and the brighter the light.

What Does CLR Stand For In Guitar Effects Pedals?

A CLR in guitar effects pedals stands for Current Limiting Resistor. This is the resistor we use to define how much current goes through the LED.

How To Find The CLR In A Schematic?

A Current Limiting Resistor (CLR) will be found immediately before the LED in the circuit schematic. In a Bill of Material (BOM), this will generally be the only component with a range of potential values.

A great example of this can be found here by taking a look at the schematic for an Optical True Bypass Switch from FuzzDog.

In this schematic, FuzzDog has suggested values between 2K2 and 4K7. This is because they don’t know what colour LED you’re using and what the forward voltage requirements of that LED are.

How To Change The LED Brightness In A DIY Effects Pedal?

In order to make an LED brighter in your DIY guitar effects pedal, you need to first find the CLR (Current Limiting Resistor) in your circuit and find out what value it is. You can do this either with a multimeter or by looking at the coloured bands. You can find my guide on understanding these, here:

Resistor Colour Band Value Calculator

Once you understand what the value of the resistor is, you can tweak it to change the brightness of the LED.

How To Make The LED Brighter In A DIY Effects Pedal?

In order to make your LEDs shine brighter in your effects pedal, you need to slightly increase the voltage to the LED by lowering the resistance. Be careful not to increase this by too much, otherwise, you could end up burning out your guitar pedal LEDs. 

If you’re not sure what resistor to use, why not use a socket so that you can easily swap out resistor values. Once you’re happy with a specific value, remove the sockets and solder the resistor in place.

How To Make The LED Less Bright In A DIY Effects Pedal?

In order to make your LEDs less bright in your DIY guitar effects pedals, you need to slightly decrease the voltage to the LED by increasing the resistance. If you increase the resistance too much and starve the LED of the voltage that it requires, you may find that the LED no longer illuminates. 

Test out a few options using a socket and once you’re happy with the brightness of your guitar pedal LED, remove the sockets from your circuit and solder the new resistor in place.

There you have it, that’s how we can change the brightness of an LED in a DIY guitar effects pedal. This is also a fantastic modification to make to a store-bought effects pedal if the LED brightness isn’t quite to your liking.

As always, happy building and if you have any questions on anything in here, please contact me.